Expandable intervertebral spacers

ABSTRACT

Laterally expanding vertebral spacer devices are provided for repairing damaged vertebral discs. The vertebral spacer devices maintain the height of a distracted vertebral disc space while providing stability to the spine. In one form of the invention, a vertebral spacer device is provided with a first arm movably coupled to a second arm. The first and second arms are laterally expandable from a first width for insertion into the disc space to a second width after insertion into the disc space. The first and second arms also define a cavity therebetween for placement of bone growth material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/182,560, now U.S. Pat. No. 6,193,757 filed Oct. 29, 1998.

BACKGROUND OF THE INVENTION

The present invention is directed to implantable devices for stabilizingthe spine. Specifically, the invention concerns intervertebral spacersexpandable from a reduced size insertion configuration to an expandedsize spacing configuration.

Intervertebral discs, located between the end plates of adjacentvertebrae, stabilize the spine, distribute forces between vertebrae andcushion vertebral bodies. An intervertebral disc may deteriorate due totrauma, aging or disease resulting in pain or discomfort to a patient.One common procedure for relief of patient discomfort is a discectomy,or surgical removal of a portion or all of an intervertebral disc.Often, this is followed by implantation of a device between adjacentvertebrae to maintain or restore disc space height. Typically,implantation of such a device is also intended to promote bony fusionbetween the adjacent vertebral bodies.

One limitation on the size of a device inserted into the disc space isthe size of the opening through surrounding tissue that is available togain access to the disc space. From a posterior approach to the spine,the dura and nerve roots must be mobilized to gain access to the discspace. Similarly, from an anterior approach, the aorta and vena cavamust be mobilized to gain access to the disc space. Such mobilization isoften limited by the anatomical structures, thus resulting in arelatively small access site. Removal of additional bone to enlarge anentrance to the disc space may weaken the joint between two adjacentvertebra. Moreover, excessive retraction of vessels and neuralstructures to create a large access opening may damage these tissues.Thus, prior procedures have been limited to placing a first devicepassable through the available opening on one side of the spine andmobilizing the tissue or vessels to place another similar implant on theopposite side of the spine. Each implant being limited in size by theavailable access site.

Thus, there remains a need for implantable devices that have a reducedsize insertion form and are expandable in the disc space to a largersize for enhancing spine stability and facilitating immobilization viabony fusion.

SUMMARY OF THE INVENTION

The present invention contemplates an intervertebral spacer device thathas a reduced size configuration for insertion into a disc space and anexpanded size configuration to maintain the spacing of the disc space.In one aspect of the present invention, the device includes a pair ofarms each having a first end and a second end, the arms being movablycoupled at their first ends. When the arms are positioned adjacent oneanother, the device is in a reduced size configuration for insertioninto the disc annulus. The device is laterally expandable in the discspace to an expanded configuration by moving the pair of arms about thefirst ends in order to increase the dimension of the deviceperpendicular to the longitudinal axis of the spine while maintainingthe inter-space distraction. Preferably, the expanded device creates acavity that may be filled with bone or bone substitute material forpurposes of promoting fusion between the adjacent vertebrae. Preferably,the height of the device in the reduced size configuration issubstantially the same as the height in the expanded configuration, withthe expanded configuration providing an increased base of support.

In another embodiment of the present invention, the first and secondarms each have laterally extending portions extending therefrom thatcooperate to engage the first and second arms to one another.Preferably, each of the laterally extending portions defines a pluralityof serrations, wherein the serrations of one laterally extending portionof the first arm cooperate in interdigiting fashion with serrations ofthe corresponding laterally extending portion of the second arm. In onepreferred embodiment, the laterally extending portions are provided atthe first and second ends of each of the arms. In another preferredembodiment, the pair of arms are pivotably coupled at their first ends,and laterally extending portions are provided at the second ends.

In still a further embodiment, the pair of arms are flexibly attachedsuch that they are compressible into a first smaller configuration andlaterally self-expand to a second larger configuration. In one suchembodiment, the arms are interconnected by a flexible hinge portion atone end of each arm. In another embodiment, each arm is flexiblyconnected to a first end portion and an opposing second end portion toform a substantially rectangular shape having flexible side walls.Preferably, the side walls are biased to assume the second largerconfiguration.

One object of the present invention is to provide a vertebral spacerdevice that is capable of insertion in a smaller form and laterallyexpandable within the disc space to an enlarged configuration forsupporting the spine.

Other objects and advantages of the present invention will be readilydiscerned upon consideration of the following written description andaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. is a perspective view of one embodiment of a vertebral spacerdevice according to the present invention.

FIG. 2 is a top view of the vertebral spacer device of FIG. 1.

FIG. 3 is a left end view of the vertebral spacer device of FIG. 2.

FIG. 4 is a right end view of the vertebral spacer device of FIG. 2.

FIG. 5 is an elevational view of the vertebral spacer device of FIG. 2.

FIG. 6 is a top view of the vertebral spacer of FIG. 1 shown in anexpanded position.

FIG. 7 is an anterior-posterior view of a pair of vertebrae having acollapsed disc space therebetween.

FIG. 8 is an anterior-posterior view of the vertebrae of FIG. 7 showingthe vertebrae after distraction of the disc space.

FIG. 9a is a partial cross-sectional top view of the vertebrae of FIG. 8with the vertebral spacer device of FIG. 1 in an expanded positionbetween the vertebrae.

FIG. 9b is a partial cross-sectional top view of a vertebral body asshown in FIG. 8, with a pair of vertebral spacer devices according toFIG. 1 inserted from a bilateral posterior approach.

FIG. 9c shows the vertebral spacer devices of FIG. 9b in an expandedconfiguration.

FIG. 10 is a side view of an insertion tool useable with the vertebralspacer devices of the present invention.

FIG. 10a is an end view of the insertion tool of FIG. 10.

FIG. 11 is a perspective view of an expansion tool useable with thevertebral spacer devices of the present invention.

FIG. 12 is a perspective view of an element of FIG. 11.

FIG. 13 is a perspective view of an alternate embodiment vertebralspacer device according to the present invention.

FIG. 14 is a top plan view of the vertebral spacer device of FIG. 13 inan unexpanded position.

FIG. 15 is a top plan view of the vertebral spacer device of FIG. 13 inan expanded position.

FIG. 16 is a cross-sectional view of the vertebral spacer device of FIG.14 taken along line 16—16.

FIG. 17 is a partial cross-sectional side view of an insertion tooldevice usable with the vertebral spacer device of FIG. 13.

FIG. 18a is a perspective view of another embodiment of a vertebralspacer device according to the present invention.

FIG. 18b is a perspective view of the vertebral spacer device of FIG.18a constrained within a delivery system.

FIG. 19a is a top view of a laterally expandable implant according toanother embodiment of the present invention.

FIG. 19b is a top view of the implant of FIG. 19a in a compressedconfiguration.

FIG. 19c is a side view of the implant of FIG. 19a.

FIG. 20a is a perspective view of another embodiment of a vertebralspacer device according to the present invention.

FIG. 20b is a perspective view of the space device of FIG. 20a withoutthe ratchet mechanism.

FIG. 21 is a perspective view of yet another embodiment of a vertebralspacer device according to the present invention.

FIG. 22 is a perspective view of yet another embodiment of a vertebralspacer device according to the present invention.

FIG. 23 is a plan view of an expansion tool usable with the vertebralspacers of FIGS. 20-23.

FIG. 23a is a fragmentary perspective view of a portion of the insertiontool device of FIG. 23.

FIG. 24 is a perspective view of another embodiment of a vertebralspacer device according to the present invention shown in a collapsedposition.

FIG. 24a is a perspective view of the vertebral spacer device of FIG. 22shown in an expanded position.

FIG. 25 is a perspective view of yet another embodiment of a vertebralspacer device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, any alterations and further modificationsin the illustrated devices, and any further applications of theprinciples of the invention as illustrated therein being contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

In accordance with one embodiment of the invention, a vertebral spacerdevice 50 is depicted in FIGS. 1-6. Device 50 includes a first lateralarm 52 and a second lateral arm 54. First arm 52 includes a first end 60and an opposite connection end 61. Second arm 54 includes a first end 62and an opposite connection end 63. First arm connection end 61 isfixedly coupled to second arm connection end 63 via connection pin 58extending through a bore 59 defined through connection ends 61 and 63.Bore 59 extends transverse to the longitudinal axis 53 of spacer 50.

First arm 52 and second arm 54 each define a portion of a top boneengaging surface 56 adapted to engage a vertebral body and a portion ofbottom bone engaging surface 57 substantially identical to top boneengaging surface 56. When first arm 52 and second arm 54 are in anopened position, as shown in FIG. 6, a central cavity 66 is definedtherebetween. Cavity 66 is adapted to receive a graft or bone-growthinducing material therein.

Referring now to FIGS. 3-6, the vertebral spacer device 50 isillustrated and described below in further detail. Connection end 63 ofsecond arm 54 is fixedly coupled to connection end 61 of first arm 52via connection pin 58 extending through bore 59. However, it should beunderstood that any type of connection mechanism contemplated herein,provide the principles of the current invention are adhered to. As anexample, but without limitation, an alternative connection mechanism maybe a hinge between and fixedly engaging first arm 52 and second arm 54to allow pivotal movement therebetween. Alternatively, first and secondarms may be integrally formed of a flexible material, thereby permittingmovement at the connection point.

First end 60 of first arm 52 and first end 62 of second arm 54 eachdefine a corresponding socket portion 64 and 65, respectively. Whendevice 50 is in a first closed position, as shown in FIG. 4, socketportions 64 and 65 define a socket for 67 for receiving a driving tool,which will be described more fully below. End 60 also includes aninternally threaded bore 68 defined by device 50. Threaded bore 68 isprovided to receive an attachment portion of an insertion toolconfigured for manipulation of device 50 into and out of a disc space.

It should be noted that in the illustrated embodiment first arm 52 andsecond arm 54 are configured such that the top bone engaging surface 56defined on each of the arms 52 and 54 extends in a substantially uniformhorizontal plane to make the bone engaging surface 56 substantiallyplanar in a first plane. The bottom bone engaging surface 57 defined byarms 52 and 54 also extends in a substantially uniform horizontal planemaking the bottom bone engaging surface 57 substantially planer in asecond plane. In a preferred embodiment, the first and second planes aregenerally parallel and separated by a height. Preferably, the heightbetween the first and second planes is substantially constant betweenthe closed position of FIG. 2 and the open positions of FIGS. 6 and 9.Thus, the disc space height during insertion may be substantiallymaintained in the expanded position.

Device 50 may be positioned in a closed position forming a reduced sizeconfiguration shown in FIGS. 2-4. Preferably, arms 52 and 54 are closelyadjacent in this position, although the exact arm positioning may varydepending on the application. In the closed position, device 50 has alateral width W₁ extending transverse to longitudinal axis 53 of thedevice.

Device 50 may be positioned in an open position forming an expanded sizeconfiguration as shown in FIGS. 1, 6 and 9. The extent of distancebetween first arm 52 and second arm 54 may be varied depending on theexpanded size desired. In the open position, device 50 may have at leasta lateral width W₂ extending transverse to longitudinal axis 53 of thedevice. Lateral width W₂ being greater than lateral width W₁. As shownin FIG. 9a, the lateral width in the expanded configuration may besubstantially greater than width W₁. This expanded width provides a muchwider base of support than the device does in the closed position. Thewider base of support provides greater stability of the device.

Referring to FIG. 9b, there is shown a vertebral body with two laterallyexpandable implants according to the present invention. Implants 70 and72, slightly smaller versions of device 50, have been inserted throughposterior openings 74 and 76, respectively, into the disc space in theirreduced size insertion form. It will be understood that this placementis approximately in the same position in the disc space into which knowndevices may be placed. In much the same manner that chairs, such as tallstools, are subject to tipping if the legs are too close, implants mayalso be subject to tipping if they lack a sufficiently wide base supportarea. However, referring to FIG. 9c, the present invention permits eachof devices 70 and 72 to be expanded in the disc space to a greaterwidth, thereby increasing the total width of the base of support.Moreover, material G promoting bone growth may be placed in the cavitybetween the arms and around the exterior of the implants.

The bone engaging surfaces 56 and 57 of device 50 are configured toprovide an even distribution and transfer of the load from the uppervertebral body through the integral side walls of device 50 to the lowervertebral body. In a preferred embodiment, the endface plates 56 and 57are knurled to provide frictional engagement between the vertebrae andthe device 50. While knurling is shown as one configuration for the boneengaging surface, other configurations may be utilized. For example, butwithout limitation, grooves may be formed on the upper and lower boneengaging surfaces extending transverse to longitudinal axis 53 to resistexpulsion. More specifically, arcuate grooves may be formed having aradius of curvature originating at pin 58 to follow the arc of the armsas they are expanded in the disc space to form the expanded openposition shown in FIG. 6.

Referring to FIGS. 7-9, a spinal segment with vertebrae V₁ and V₂ isillustrated to briefly describe a surgical procedure in which device 50may be employed. More specifically, in FIG. 7 a damaged or diseasedspinal segment is shown without the device 50. D1 represents adegenerated or damaged disc between vertebrae V₁ and vertebrae V₂ thathas resulted in the collapse of the disc space between the vertebrae.Vertebrae V₁ and V₂ form part of a spinal column having a longitudinalaxis L extending therethrough.

In FIG. 8, the vertebrae V₁ and V₂ are shown distracted such that thedisc space is restored to approximately its normal height, representedby distracted disc space D2. Tensioning of annular structures thatextend between D1 and D2 promotes disc stability. Also shown is anopening A made in the annulus fibrosus that may be created by thesurgeon by an annulotomy or disectomy surgical procedure to gain accessto the disc space from an anterior approach. As known in the art and notfurther described herein, the adjacent end plates of V₁ and V₂ may beprepared to promote bone fusion therebetween and accept device 50.Device 50 is inserted through opening A while in the reduced sizeconfiguration (as shown in FIGS. 2 through 4). Once inserted into thedisc space, the device 50 is laterally expanded to expanded sizeconfiguration (as shown in FIGS. 1 and 6) by moving first arm 52 inrelation to second arm 54 in the disc space. The lateral expansion ofdevice 50 increases the lateral dimension of device 50 in a directiontransverse to longitudinal axis L, while maintaining the height ofdistracted disc space D2. In FIG. 9 the device 50 is shown in plan viewinserted into D2 between vertebrae V₁ and V₂ through opening A. It willbe understood that use of the laterally expandable implant according tothe present invention limits the amount of mobilization of overlappingvessels and permits insertion of an implant having a much wider spacingconfiguration than would otherwise be implantable with a non-expandingimplant.

The expanded configuration of device 50 creates cavity 66 that may thenbe filled with a bone graft material or bone-growth inducing material Gfor the purposes of promoting fusion between vertebrae V₁ and V₂. Thegraft material G also helps to maintain the device 50 in the laterallyexpanded configuration. As can be seen in FIG. 9, the expanded device 50is larger than the opening A made through the annulus fibrosus. Thus, inaddition to the knurled endface plates 56 and 57, the remaining annulusfibrosis may also act to limit displacement of device 50 from the discspace. While the device has been inserted with the wider end adjacentopening A, it is contemplated that the connection end may be disposedadjacent the opening. For this use, a biasing element, such as a spring,may be disposed between the arms to urge them to the expanded condition.

FIGS. 7-9c illustrate two methods for inserting laterally expandabledevices into the disc space D2. The present invention also contemplatesthe use of additional methods as known in the art for insertinginterbody fusion implants. For example, more than one vertebral spacerdevice may be inserted through the same opening A. For example, a firstdevice 50 could be inserted and laterally expanded, and packed with bonegraft material. Then a second device may be inserted in the disc spaceand between the arms of the first device. The second device may belaterally expanded and packed with bone graft material G.

Referring to FIGS. 9a and 9 b, there is shown a vertebral body with twoimplants positioned in the disc space. In this procedure, bilateralaccess to the disc space is achieved by posterior openings 74 and 76. Itwill be understood that the size of openings may be limited by theamount of dural compression that may be safely achieved, nerve rootlocation and the amount of bone removed adjacent the disc space. Devices70 and 72 are inserted via opening 74 and 76, respectively. The devicesare inserted into the disc space in the reduced size configuration. Oncedisposed in the disc space, devices 70 and 72 are expanded and graftmaterial is positioned in the cavity formed between the arms.Preferably, as shown in FIG. 9c, material may be positioned between theimplants before one or both are expanded to provide a further area forbone growth. While a device according to FIG. 1 has been shown for thepurposes of illustrating the methods of insertion, it is contemplatedthat the other embodiments disclosed herein may be inserted in a likemanner.

Referring now to FIGS. 10-12, various instruments useful for insertionand lateral expansion of device 50 are shown therein. The insertion tool260 of FIG. 10 is useable for insertion of device 50 into the discspace. Insertion tool 260 includes a handle portion 262, a threaded stemportion 266, and rod 264 extending between handle 262 and threadedportion 266. A sleeve 268 is slidably disposed about the stem 264.Sleeve 268 includes protrusion 270 extending therefrom and adapted toengage cavity 67 in device 50. While not illustrated, device 260 mayinclude a stop mechanism operable to prevent sliding of sleeve 268 aboutrod 264 after device 50 is engaged thereto.

To use insertion tool 260 to insert the implant device 50, threadedportion 266 threadedly engages device 50 via threaded bore 68. Once thedevice 50 is threadedly engaged to insertion tool 260, sleeve 268 may beslid down rod 264 toward the device 50 until protrusion 270 resideswithin cavity 67. Rod 264 and protrusion 270 prevent rotation betweendevice 50 and insertion tool 260 during insertion. The vertebral spacerdevice 50 may then be inserted into a prepared disc space using theinsertion tool 260. Once device 50 is placed in the disc space, sleeve268 may be retracted towards handle 262 to disengage protrusion 270 fromcavity 67. Threaded stem portion 266 may then be removed from threadedbore 68. Alternatively, if it is desired to remove the device 50 fromthe disc space after initial insertion or to reposition the device 50within the disc space, the threaded stem portion 266 allows the device50 to be withdrawn or repositioned. It is contemplated herein thatinsertion of device 50 into the disc space via insertion tool 260 isaccomplished with device 50 in a closed position, as shown in FIG. 2.

Once the device 50 is inserted into the desired position in the discspace, first arm 52 and second arm 54 may be laterally expanded toincrease the lateral dimension of device 50 with respect to spinallongitudinal axis L in order to stabilize the spinal column and fill alarger portion of the disc space. In a preferred embodiment, each boneengaging surface 56 and 57 includes a beveled edge around the perimeterof device 50. The beveled edge facilitates insertion between adjacentvertebrae and eases expansion in the disc space.

FIG. 11 illustrates one type of driving tool 250 operable to at leastinitially laterally expand device 50 to a laterally expandedconfiguration. Driving tool 250 includes T-handle portion 254, a squaredriving end 258 adapted to engage cavity 67, and a hollow tube 256extending between handle portion 254 and driving end 258. In order tolaterally expand device 50, driving tool 250 is rotated via the T-handle254 with driving end 258 disposed within cavity 67. Rotation of drivingend 258 causes first arm 52 and second arm 54 to move laterally withrespect to one another in a manner that laterally expands the arms 52and 54 of device 50.

In order to further laterally expand first arm 52 and second arm 54, aspreader 280 as shown in FIG. 12 may be used in conjunction with tool250. Spreader 280 includes a first end 282, a wedge portion 286, andstem 284 extending therebetween. As shown in FIG. 11, spreader 280 maybe disposed within hollow tube 256 and advanced beyond its distal end tomore fully expand the device. Wedge portion 286 may be placed betweenfirst arm 52 and second arm 54. A force applied to first end 282 driveswedge portion 286 between arms 52, 54 in order to further laterallyexpand the device 50.

While the above-described spreader is disclosed as a preferredembodiment, it is contemplated that other instruments may be used toexpand the device without deviating from the scope of the invention.Specifically, spreader 280 may be used may be used alone to laterallyspread the expandable device.

As shown in FIGS. 6 and 9, when device 50 is in a laterally expandedposition, a cavity 66 is formed between first arm 52 and second arm 54.A graft material G may then be placed or packed into cavity 66. Thegraft material G could be cancellous bone or bone chips, or a suitablebone graft substitute material known to those skilled in the art. Oneadvantage of the device 50 is that it allows bone graft material G to beplaced at or near the central portion of the vertebrae while theexpandable spacer engages more lateral portions of the vertebra. Thiscentral portion is known to be highly vascular and biologically active,so that it is an excellent location for bone graft incorporation andfusion. In addition, bone-growth enhancing materials may be introducedwith the graft material to enhance initial and ultimate fusion of thevertebrae V₁ and V₂.

It should be appreciated that device 50 may be delivered to the discspace for insertion through a cannula employed in a minimally-invasivesurgical technique. Device 50 is sized for placement through the cannulain its unexpanded configuration. Once positioned in the disc space, thelateral dimension of the device is increased by expanding the first andsecond arms 52, 54 as described above. Other surgical techniques forinsertion are contemplated, for example, open surgical procedures withdirect access to the spine. Device 50 thus allows minimization of thesize of the entry into the disc space and the resulting damage to tissuesurrounding the surgical site. Further, the reduced size configurationof the implant permits insertion of a relatively large spacer whereanatomical features, such as the dura, nerve roots or blood vessels,would have prevented placement of a larger, non-expanding sized spacer.

Referring now to FIGS. 13-16, another embodiment of the presentinvention is illustrated. The expandable vertebral spacer 80 includes afirst arm 82 having a distal end 90, and a second arm 84. Second arm 84is movable coupled to main body portion 82 via hinge portion 98. Firstarm 82 is provided with a tapering guide 88 protruding therefrom as itextends from hinge portion 98 towards distal end 90. Guide 88 isreceived within a recess 86 defined in second arm 84. Vertebral spacer80 also defines tool receiving opening 99 defined in hinge 98. Toolreceiving opening 99 is configured to have an internal thread toaccommodate an insertion tool, such as tool 300 illustrated in FIG. 17.

Second arm 84 includes a locking arm 94 adjacent its distal end that isintegrally formed with laterally expandable portion 84 via locking armhinge portion 95. Locking arm 94 is configured to be positioned adjacentdistal end portion 90 in the closed position shown in FIG. 14. In theclosed position the device is in a reduced size configuration suitablefor insertion. In this configuration, device 80 has a lateral width W₃extending transverse to the longitudinally axis of the device.Preferably, spacer 80 is formed of an at least partially resilientmaterial and distal end portion 90 may be biased toward cavity 85. Inthis configuration the arms tend to move to the locked position once thespacer is sufficiently expanded. Distal end portion 90 includes a catch92 formed thereon, and locking arm 94 includes a catch-receiving portion96. When the device 80 is laterally expanded to a second lateralposition, as shown in FIG. 15, locking arm hinge 95 urges locking arm 94towards distal end portion 90 until catch-receiving portion 94 engagescatch 92. Catch 92 prevents displacement of expandable portion 84towards main body portion 82 after the device 80 is inserted in the discspace. The device 80 is then held in the expanded position, and cavity85 may be packed with bone growth material through opening 99. Furtheropenings for bone ingrowth or bone growth material packing may beprovided. In the laterally expanded configuration of FIG. 15, device 80has a maximum lateral width W₄, width W₄ being greater than W₃.

It should be noted that the device 80 defines a top vertebral bearingsurface 97 and a bottom vertebral bearing surface 93. The bearingsurfaces 93 and 97 are composed of the surfaces provided on first arm82, second arm 84, and hinge 98. In a preferred embodiment, bearingsurfaces 93 and 97 are spaced apart a height that remains relativelyconstant from the closed to expanded positions. The bearing surfacescontact the adjacent vertebrae endplates to provide an even distributionof loads through the endplates and balanced loading conditions. Whilenot shown, it will be understood that these surfaces may includeroughening to inhibit expulsion.

It is contemplated that devices according to the present invention maybe manufactured from bio-compatible materials having at least someflexibility without fracture. Further, it is anticipated that portionsof bone may be used provided the hinge points have been at leastpartially demineralized to provide flexibility. Demineralization of boneis known in the art and will not be described further herein. Morepreferably, device 80 is formed from material having a degree ofresiliency tending to urge locking arm 94 into the locking position withthe catch 92 engaged with catch-receiving portion 94. Such materials mayinclude, but are not limited to, stainless steel, shape memory alloys,composites and plastics. Moreover, while flexible hinge portions havebeen disclosed, it will be understood that hinge pin and channelconnections may replace the flexible hinges without deviation from thespirit of the invention. Optionally, a biasing mechanism, such as aspring, may be placed between the arms to urge the device to theexpanded configuration.

The present invention also contemplates an instrument for inserting andexpanding an implant according to the present invention. Referring nowto FIG. 17, an insertion tool 300 is illustrated. Tool 300 includes ahollow outer sleeve 302 that receives a portion of an inner sleeve 304.Inner sleeve 304 defines connecting portion 322 that engages matingportion 320 of outer sleeve 302. In the illustrated embodiment, innersleeve 304 is threadedly received within the outer sleeve 302. Innersleeve 304 further defines an opening 324 therethrough for receiving rod310. Inner sleeve 304 also includes a pair of movable arms 306 and 308having gripping portions 309 and 311, respectively, configured forholding device 80 during insertion. In order for arms 306 and 308 togrip the device 80, outer 302 is moved with respect to inner handle 304such that inclined portion 318 of outer sleeve 302 urges grippingportions 309 and 311 of arms 306 and 308 against device 80. In theillustrated device 300, this accomplished by rotating outer handle 302about a thread on connecting portion 322 towards the device 80.

Once device is engaged by gripping portions 309 and 311, it may beinserted into the disc space. After insertion of device 80 to thedesired location, rod 310 is operable to laterally expand device 80. Rod310 has a handle portion 312, and opposite a threaded portion 314, and ashaft 313 extending therebetween. In a preferred embodiment, shaft 313has a distal end 316 that is beveled to engage the inclined surfaces 87and 89 of first arm 82 and second arm 84, respectively. Handle 310 maybe engaged with device 80 during insertion into the disc space viathreaded engage with tool receiving opening 99. The threaded engagementbetween threaded portion 314 and the device 80 allows the device 80 tobe positioned within the disc space. In order to position the device 80to its expanded configuration, mechanism 310 is threaded withinreceiving portion 99 in order to urge distal end 316 against surfaces 87and 89 to laterally expand device 80 to the expanded or second lateralconfiguration as shown in FIG. 15.

While the above-described spacer embodiments of FIGS. 1 and 13 have beendescribed as having a first arm and a second arm movable coupled, itwill be understood that the invention contemplates a main body portionand laterally expandable portion movably coupled thereto. Specifically,while first arm and second arm may simultaneously move laterally to formthe expanded configuration, it is contemplated that one arm may remainstationary while the other arm moves. Moreover, the device may be formedsuch that the device includes a stationary main body with one or moremovable laterally expandable portions movable to give the device both areduced size configuration and a laterally expanded size configuration.

Referring now to FIGS. 18a and 18 b, another embodiment of the presentinvention is illustrated. Vertebral spacer device 100 includes a pair oflateral arms 102 and 103 extending between a distal end 106 and aproximal end 108. The device 100 includes a top vertebral bearingsurface 112 and an identical bottom vertebral bearing surface (notshown). A central cavity 114 is formed between the lateral arms 102. Thedevice 100 also includes openings 104 and 105 defined by lateral arms102 and 103, respectively. Openings 104 and 105 permit communicationbetween the interior and exterior of the device and reduce the materialin walls 102 and 103, thereby increasing the flexibility of device 100.Device 100 also includes at least one insertion tool opening 110 formedin proximal end 108. Preferably, opening 110 is threaded to receive acorrespondingly threaded insertion tool (not shown).

The embodiment of FIG. 18 is preferably formed of a resiliently flexiblematerial. Such materials may include, without limitation, bio-compatiblemetals (including shape memory alloys), composites, and plastics. In apreferred embodiment, the device 100 is expanded and contracted bymaking the device 100 from a shape memory material, such as nitinol,exhibiting super elasticity and/or temperature induced shape memory. Thedevice 100 is initially formed in a laterally expanded or secondposition. In order to insert the device 100 through a small opening andinto the disc space, it is contracted to a first lateral position byapplying a force to lateral arms 102 and 103 in the direction indicatedby the arrows “R”. Thus, the device is laterally compressed into asmaller sized configuration. Often, the device will experience someelongation, as shown by dimension “I”. When the device is contracted, asshown in FIG. 19, it may be inserted through a tubular delivery system,such as the cannula 120. Once the device is inserted in the disc space,it is no longer confined by the cannula 120, and it self-expandslaterally to a second position within the disc space approximating itspre-insertion condition. Cavity 114 may be filled with bone growthmaterial delivered through opening 110. Cavity 114 may also be partiallyloaded with bone growth material prior to insertion. It is alsocontemplated herein that device 100 may be inserted into the disc spacewithout use of cannula 120, such as by an open surgical procedure.Temporary compression may be achieved by an external device such as, butwithout limitation, pliers adapted to compress the implant.

FIGS. 19a through 19 c illustrate a further embodiment of a laterallyexpandable spacer according to the present invention. Spacer 121includes arms 122 and 123 connected by a flexible portion. Arm 122terminates in an end wall 125 and arm 123 terminates in an end wall 126.As shown in FIG. 19b, the respective lengths of arms 122 and 123 allowend wall 126 to nest within end wall 125.

Spacer 121 is preferably formed of a flexible and resilient material.The spacer is in a relaxed form in the expanded configuration of FIG.19a having a lateral width W₆. Width W₆ is decreased to lateral width W₅by the application of compressive force on arms 122 and 123 urging endwalls 125 and 126 towards one another. Preferably, spacer 121self-expands from the reduced size configuration of FIG. 19b to theexpanded configuration of 19 a. Preferably W₆ is approximately twice W₅,although a greater or lesser amount of lateral expansion may beprovided. Preferably, spacer 121 is formed of a fiber reinforced polymercomposite. The fibers, shown by the parallel shading marks in FIGS. 19athrough 19 c, extend generally parallel to the length of side walls 122and 123. It will be understood that this arrangement of fibers providesa degree of flexibility between the arms but resists compression fromthe upper to lower surfaces engaging the vertebral bodies.

Referring to FIG. 20a, another embodiment of a vertebral spacer deviceis illustrated. Vertebral spacer device 130 includes a first arm 132 anda second arm 134 fixedly connected via hinge portion 136. In thisembodiment, hinge portion 136 is integrally formed with first arm 132and second arm 134. First arm 132 includes first lateral extendingportion 138, and second arm 134 includes a second laterally extendingportion 140. First laterally extending portion 138 includes firstserrations 139 and second laterally extending portion 140 includescorresponding second serrations 141 disposed adjacent first serrations139. Serrations 139 and 141 cooperate in interdigiting fashion torestrain lateral contracting of the first arm 132 with respect to thesecond arm 134. The device 130 also includes tool opening 142, whichallows engagement of device 130 to insertion and/or expansion tools. Aspreviously disclosed, opening 142 may be threaded to receive acorresponding threaded tool. As with earlier disclosed embodiments,device 130 also defines a cavity 146, and includes substantially planarvertebral bearing surfaces 148 and 149 for engaging respective endplates of adjacent vertebrae.

The device 130 is shown in a contracted position, and once inserted thedevice may be expanded by applying a force in the direction of thearrows “R”. The interdigiting serrations 139 and 141 must yieldsufficiently to allow movement of first arm 132 with respect to secondarm 134, while maintaining the separation of arm 132 and second arm 134when the force is removed.

FIG. 20b represents a modified version of FIG. 20a lacking serrations139 and 141. Preferably, spacer 130 is formed of a flexible materialthat may be plastically deformed. Thus, force applied to arms 132 and134 to expand the device plastically deforms hinge portion 136. Plasticdeformation of hinge portion 136 maintains the device in the expandedcondition.

FIG. 21 illustrates another embodiment of the vertebral spacer device ofthe present invention. Device 150 includes a first arm 152 and a secondarm 154. The term arm as used throughout the disclosure is used broadlyto define sections and portions of devices. Arms may not necessarilymove within a device configuration. First arm 152 includes a firstextension 158 and a second extension 155. Second arm 154 includes thirdextension 156 and fourth extension 166. First arm 152 is sized toreceive extensions 156 and 166 within extensions 158 and 155. Firstextension 158 defines first serrations 159 and second extension definessecond serrations 161. Third extension 156 defines third serrations 157and fourth extension 166 defines fourth serrations 168. First serrations159 and third serrations 157 cooperate in interdigiting fashion incooperation with interdigiting engagement of second serrations 161 andfourth serrations 168 to maintain lateral spacing between first arm 152and second arm 154. Device 150 also defines an upper vertebral engagingsurface 164, and an identical lower vertebral engaging surface, and toolopenings 160. Device 150 also defines a cavity 162, which may be filledwith bone growth material. Once the device 150 is inserted into the discspace, it may be expanded by applying force in the direction indicatedby arrow “R” to move first arm 152 with respect to second arm 154.

Referring now to FIG. 22, yet another embodiment of a vertebral spacerdevice in accordance with the present invention is illustrated. Device170 includes a first arm 172 and a second arm 174. First arm 172includes first a pair of extensions 176 and second arm 174 includes apair of extensions 178. Extensions 176 include projections 175, andextensions 178 define receptacles 177. Projections 175 are configured tobe placed within a respective one of receptacles 177. Projections 178define first serrations 179 thereon, and receptacle 177 define secondserrations 181 thereon. First serrations 179 and second serrations 181cooperate in interdigiting fashion to resist displacement at first arm172 with respect to second arm 174. However, first serrations 179 andsecond serrations 181 yield sufficiently to allow lateral expansion ofthe device 170. Device 170 includes an upper vertebral engaging surface186 and an identical lower vertebral engaging surface. Arms 172 and 174define a central cavity 182 for receiving bone growth material.

A tool 340 for expanding the devices illustrated in FIGS. 20-22 isillustrated in FIGS. 23 and 23a. Tool 340 includes a first lever 350pivotably coupled to a second lever 360 by pin 346. First lever 350includes a first handle portion 351 pivotably coupled to a firstextension 353 via pin 352. Second lever 360 has a second handle portion361 pivotably coupled to a second extension 363 via pin 362. Extensions353 and 363 are pivotable engaged via pin 348. Handle 340 also includesratchet mechanism 342 coupled to one of the handle portions 351, 361. Inthe illustrated embodiment, ratchet mechanism 342 is coupled to secondhandle portion 361 via pin 344. Ratchet mechanism 342 has teeth 346 forengaging first handle portion 351. Ratchet mechanism 342 is operable tomaintain the relative spacing between handle portions 351 and 361 whenengaged thereto.

First extension 353 has a first engagement portion 354 and secondextension 363 has a cooperable second engagement portion 364 located atrespective distal ends of each extension 353 and 363. First engagementportion 354 includes a first coupling 356, and second engagement portion364 includes a second coupling 366, each for coupling respective leverarms 350 and 360 to a vertebral spacer device, such as device 150illustrated in FIG. 21. Couplings 356 and 366 extend through acorresponding one of tool openings 160 to engage the device 150. Asshown in detail in FIG. 23a with respect to first engagement portion354, first and second couplings 356 and 366 each include a first andsecond head 358 and 368 and a first and second recess 359 and 369,positioned between first and second extensions 353 and 363,respectively. The first and second recesses 359 and 369 are configuredto receive a portion of the arms 152 and 154 therein to allow head 358and 368 to engage the device 150. The device 150 may then be laterallyexpanded or contracted as needed by manipulation of first and secondlever arms 351 and 361. Tool 340 may then be uncoupled from device 150by withdrawing the first and second coupling 356 and 366 from device150.

Referring now to FIGS. 24-24a, another embodiment of a vertebral spacerdevice according to the present invention is illustrated. Device 190includes first arm 192 and second arm 194. First arm 192 is pivotallycoupled to second arm 194 via sidewalls 196 extending therebetween. Inthe illustrated embodiment, two sidewalls 196 are shown with one at theproximal end of the device 190 and the other sidewall 196 at the distalend of device 190. The first and second arms 192 and 194 are engaged tosidewalls 196 via hinge pins 197. The device 190 also defines an uppervertebral engaging surface 200 and a lower vertebral engaging surface,and tool insertion openings 198. In one embodiment, the device 190 isprovided with ridges 204 extending from vertebral engaging surfaces forengaging the adjacent vertebral endface plates. A central cavity 202 forreceipt of bone growth material is defined by the sidewalls 96, firstarm 192, and second arm 194.

As shown in FIG. 24, the device 190 is collapsible to a first reducedsize configuration for insertion into the disc space having a lateralwidth W₇. Once the device is inserted, it may be pivoted about hingeportions 197 to an expanded position having greater width W₈ as shown inFIG. 24a. The device may be expanded by a tool inserted through one ormore of the openings 198. Bone growth material may be placed in cavity202 through openings 198.

Another embodiment of the vertebral spacer device of the presentinvention is illustrated in FIG. 25. The vertebral spacer device 210includes a first arm 212 and a second arm 214. First arm 212 includes afirst laterally extending portion 215, and second arm 214 includes asecond laterally extending portion 216. Second arm 214 also includesoffset portion 217 extending to engage first arm 212 at connection 226.Preferably, connection 226 is a hinge-type connection. The device 210also includes vertebral engagement surfaces 220 and 221 and, in apreferred embodiment, ridges 224 for engaging vertebral endface platesafter insertion. A central cavity 222 is formed between first arm 212and second arm 214. Bone growth material may be placed in central cavity222. Openings 218 may also be provided in the device for receivingvarious tools for inserting and expanding the device. A force applied inthe direction indicated by the arrows “R” will act to expand the device210 from the first reduced size lateral position of FIG. 25 to a secondexpanded lateral position (not shown) after insertion of the device 210into the disc space.

The vertebral spacers of the present invention may be placed andmaintained in position within the disc space by additional fixation. Thevertebral spacer devices are generally retained in position by thecompressive forces of the vertebral bodies acting on the bone engagingsurfaces of the implant. The spacer devices are preferably configured totransmit the compressive forces from the upper vertebral body directlythrough a one-piece side wall to the lower vertebral body and to limitconcentration of compressive loads at the movable couplings of the arms.Moreover, it is contemplated herein that fixation devices may be used inconjunction with the vertebral spacer device of the present invention.Alternatively, the vertebral spacer devices may be provided with anopening for receiving a fixation device, such as a bone screw, allowingthe vertebral spacer to be attached to adjacent vertebrae. Moreover, itis contemplated that the bone engaging surfaces may be configured,without limitation, to be tapered, concave or convex in order toapproximate the disc space. More specifically, upper and lower boneengaging surfaces may define an angle therebetween for enhancinglordosis of the spine.

Preferably, implants according to the present invention may have lengthsvarying from 20 mm to 26 mm. Further, implants may have reduced sizeinsertion configurations with widths varying preferably between 16 mmand 20 mm. Although these dimensions may be used, larger or smallerdimensions may be used without deviating from the scope of theinvention.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications the come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. A method for maintaining a longitudinalintradiscal space between two adjacent vertebrae, the method comprising:providing a vertebral spacer having a first portion moveably coupled toa second portion at a connection end of the vertebral spacer, the firstportion being separate from the second portion at a first end of thevertebral spacer opposite said connection end, the first portion and thesecond portion defining a socket at the first end, the first portion andsecond portion moveable between an insertion configuration and anexpanded spacer configuration; coupling a tool to the socket at thefirst end; inserting the vertebral spacer into the disc space with thevertebral spacer in the insertion configuration; and moving thevertebral spacer into the expanded configuration.
 2. The method of claim1, further comprising packing bone growth material between the firstportion and second portion when the vertebral spacer is in the expandedspacer configuration.
 3. The method of claim 1, wherein said movingincludes rotating the tool to move the vertebral spacer to the expandedspacer configuration.
 4. The method of claim 1, wherein: the toolincludes a rod with a threaded stem portion and a sleeve slidablydisposed about the rod, the sleeve having a protrusion extendingtherefrom; and wherein said coupling includes threadedly engaging athreaded bore in the vertebral spacer with the threaded stem portion andinserting the protrusion into the socket.
 5. The method of claim 4,further comprising disengaging the protrusion from the socket after saidinserting.
 6. The method of claim 5, further comprising removing thethreaded stem portion from the threaded bore.
 7. The method of claim 6,wherein said moving includes inserting an insertion tool into the socketand rotating the insertion tool to move the vertebral spacer to theexpanded configuration.
 8. The method of claim 1, wherein the toolincludes a wedge portion and said moving includes driving the wedgeportion between the first portion and the second portion.
 9. The methodof claim 1, wherein said moving includes driving a wedge portion of aspreader between the first portion and the second portion.
 10. Themethod of claim 1, wherein said providing includes furnishing the firstportion with a first laterally extending portion and the second portionwith a second laterally extending portion, the first laterally extendingportion and the second laterally extending portion defining the socket.11. The method of claim 1, wherein each of the first and second portionsdefine a top bone engaging surface adapted to engage one of the adjacentvertebrae and a bottom bone engaging surface adapted to engage the otherof the adjacent vertebrae.
 12. The method of claim 1, wherein saidmoving includes laterally expanding the vertebral spacer within thelongitudinal intradiscal space between the two adjacent vertebrae.
 13. Amethod for maintaining a longitudinal intradiscal space between twoadjacent vertebrae, the method comprising: providing a vertebral spacerhaving a first arm moveably coupled to a second arm at a first end ofthe vertebral spacer, the first arm having an end portion integrallyformed at a second end of the vertebral spacer opposite said first end,the second arm having a locking arm integrally formed at the second endof the vertebral spacer, the first portion and second portion beingmoveable between an insertion configuration and an expandedconfiguration, the locking arm being biased to lock with the end portionwhen the vertebral spacer is in the expanded configuration; insertingthe vertebral spacer in the insertion configuration into the intradiscalspace; and moving the vertebral spacer into the expanded configurationuntil the vertebral spacer is locked into the expanded configurationwith the locking arm.
 14. The method of claim 13, wherein each of thefirst and second arms define a top bone engaging surface adapted toengage one of the adjacent vertebrae and a bottom bone engaging surfaceadapted to engage the other of the adjacent vertebrae.
 15. The method ofclaim 13, wherein said moving includes laterally expanding the vertebralspacer within the longitudinal intradiscal space between the twoadjacent vertebrae.
 16. The method of claim 13, wherein said movingincludes engaging a catch formed on the end portion with acatch-receiving portion formed on the locking arm.
 17. The method ofclaim 13, further comprising: providing a tool having a pair of moveablegripping arms and a threaded shaft; gripping the vertebral spacerbetween the moveable gripping arms before said inserting; threading thethreaded shaft into a tool receiving opening defined in the vertebralspacer; and wherein said moving includes expanding the vertebral spacerby advancing the threaded shaft against a tapered guide formed on thevertebral spacer in a spacer between the first and second arm.
 18. Themethod of claim 13, wherein the locking arm and end portion each haveserrations that lock the vertebral spacer in the expanded configuration.19. The method of claim 13, further comprising packing bone growthmaterial between the first arm and second arm when the vertebral spaceris in the expanded configuration.
 20. A method for maintaining alongitudinal intradiscal space between two adjacent vertebrae, themethod comprising: providing a vertebral spacer formed from aresiliently flexible material, the spacer having a pair of resilientlateral members coupled together at both ends, the pair of lateralmembers being resiliently biased to laterally expand from an insertionconfiguration to a laterally expanded configuration; compressing thelateral members to the insertion configuration; inserting the spacerinto a tubular delivery system; delivering the spacer into theintradiscal space; and through the tubular delivery releasing the spacerso that the spacer laterally expands within the longitudinal space tothe expanded configuration in which each lateral member contacts both ofthe adjacent vertebrae.
 21. The method of claim 20, further comprisingpacking bone growth material between the lateral members when thevertebral spacer is in the expanded configuration.
 22. A method formaintaining a longitudinal intradiscal space between two adjacentvertebrae, the method comprising: providing a vertebral spacer having afirst arm and a second arm, the first arm having a pair of firstextensions with first serrations provided thereon, the second arm havinga pair of second extensions having second serrations provided thereonthat engage the first serrations, the first arm and second arm beingmoveable between an insertion configuration and a laterally expandedconfiguration, the first and second serrations cooperate in aninterdigiting fashion to resist displacement and yield sufficiently toallow expansion of the spacer; inserting the vertebral spacer in theinsertion configuration into the intradiscal space in which each of thearms are oriented to contact both of the adjacent vertebrae; and movingthe vertebral spacer into the laterally expanded configuration.
 23. Themethod of claim 22, further comprising: providing a tool having a firstengagement portion and a second engagement portion; coupling the firstengagement portion to the first arm and the second engagement portion tothe second arm; and wherein said moving includes spreading the first andsecond engagement portions apart.
 24. The method of claim 22, furthercomprising packing bone growth material into a cavity between the firstarm and the second arm when the vertebral spacer is in the expandedconfiguration.
 25. The method of claim 22, wherein said moving includesapplying force on both the first arm and the second arm to overcomeresistance between the serrations.
 26. The method of claim 22, whereinthe first arm is sized to receive the pair of second extensions of thesecond arm.
 27. The method of claim 26, wherein the first extensionseach have a projection with the first serrations provided thereon andthe second extensions each have a receptacle with the second serrationsdefined therein.